Coloring recording materials based on a coloring system consisting of a coloring dye which gives rise to a color by an action of developer though itself is colorless or has almost no color (hereinafter referred to "coloring dye") and a developer coloring the dye are used for, for instance, pressure sensitive copying paper, thermographic recording paper, prepaid cards or POS (point of sales) labels. Their applications are expanding.
A large number of proposals have been offered with regard to fluoran compounds as coloring dyes used for these coloring recording materials, and the fluoran compounds are used in a large amount in the market as well.
Out of the fluoran compounds, those having an anilino group at the 2 position and a methyl group at the 3 position as substituents and a substituted amino group at the 6 position are important as black coloring dyes, are a mainstream of the current market, and have a large number of proposals. That is, compounds having all alkyl groups for all the substituents of the said substituted amino group were proposed in U.S. Pat. No. 3,681,390, etc. Compounds having a cyclohexyl group and lower alkyl group as the substituents of the said substituted amino group are proposed in U.S. Pat. No. 4,410,708, etc. Compounds having a cyclohexyl group and an alkyl group having 5 to 8 carbon atoms are proposed in Japanese open patent No. Sho 60-35053.
However, the coloring performance of these known fluoran coloring dyes is not satisfactory yet. Particularly the improvement of the storability of the dyes is very desired.
The object of this invention is to provide coloring dyes with excellent coloring performance and storability, or coloring dyes with excellent solvility required when used for pressure sensitive copying paper.